The electrostatographic process, and particularly the xerographic process, is known. This process involves the formation of an electrostatic latent image on a photoreceptor, followed by development of the image with a developer, and subsequent transfer of the image to a suitable substrate. In xerography, the surface of an electrophotographic plate, drum, belt or the like (imaging member or photoreceptor) containing a photoconductive insulating layer on a conductive layer is first uniformly electrostatically charged. The imaging member is then exposed to a pattern of activating electromagnetic radiation, such as light. The radiation selectively dissipates the charge on the illuminated areas of the photoconductive insulating layer while leaving behind an electrostatic latent image on the non-illuminated areas. This electrostatic latent image may then be developed to form a visible image by depositing finely divided marking particles on the surface of the photoconductive insulating layer. The resulting visible image may then be transferred from the imaging member directly or indirectly (such as by a transfer or other member) to a print substrate, such as transparency or-paper. The imaging process may be repeated many times with reusable imaging members.
U.S. Pat. No. 6,767,684 to Patel et al. describes an emulsion aggregation process for forming toner that combines both a latex containing a cross-linked resin and a latex containing a resin free of cross-linking. The process comprises, inter alia, mixing a colorant dispersion comprising an acicular magnetite dispersion and a colorant with a latex containing a cross-linked resin, a latex containing a resin free of cross-linking, a wax dispersion, and a coagulant; heating the resulting mixture below about the glass transition temperature (Tg) of the latex resin to form toner sized aggregates; adding to the formed toner aggregates further resin latex; adding a base to adjust the pH; and heating the resulting aggregate suspension to permit fusion or coalescence of the toner aggregates and to obtain smooth particles. In each of the Examples, the latex added after the formation of toner sized aggregates was non-cross-linked latex.
U.S. Pat. No. 5,763,132 to Ott et al. describes a process for decreasing toner adhesion and decreasing toner cohesion, which comprises adding a hard spacer component of a polymer of polymethyl methacrylate (PMMA), a metal, a metal oxide, a metal carbide, or a metal nitride, to the surface of a toner comprised of resin, wax, compatibilizer, and colorant excluding black, and wherein toner surface additives are blended with said toner, and wherein said component is permanently attached to the toner surface by the injection of said component in a fluid bed milling device during the size reduction process of said toner contained in said device, and where the power imparted to the toner to obtain said attachment is from equal to, or about above 5 watts per gram of toner. See the Abstract and column 1, lines 9-28.
U.S. Pat. No. 5,716,752 to Ott et al. describes a process for decreasing toner adhesion and decreasing toner cohesion, which comprises adding a component of magnetite, a metal, a metal oxide, a metal carbide, or a metal nitride to the surface of a toner comprised of resin, wax, and colorant, and wherein toner surface additives are blended with said toner, and wherein said component is permanently attached to the toner surface by the injection of said component in a fluid bed milling device during the size reduction process of said toner contained in said device, and where the power imparted to the toner to obtain said attachment is from equal to, or about above 5 watts per gram of toner. See the Abstract.
Having spacer-particles enables toner and developer including such toner to exhibit reduced toner cohesion, improved flow and transfer efficiency stability and hence excellent development and transfer stability during copying/printing in xerographic imaging processes, and minimized development falloff, for example including maintaining DMA (developed mass per area on a photoreceptor), TMA (transferred mass per area from a photoreceptor), and/or triboelectric charging characteristics for an extended number of imaging cycles.